Changes in the neurotransmitter profile in the central nervous system of marine medaka (Oryzias melastigma) after exposure to brevetoxin PbTx-1 - A multivariate approach to establish exposure biomarkers.

A strategy to construct multivariate biomarkers for exposure to algal neurotoxins via correlating changes to the profiles of a series of neurotransmitters and their metabolites in the central nervous system (CNS) of exposed test organism is reported. 3-Month-old marine medaka (Oryzais melastigma) were exposed to waterborne brevetoxin PbTx-1 at two sub-lethal dose levels (0.5 and 2.5 µg-PbTx-1 L-1) for a duration of 12 h before quantification of 43 selected neurotransmitters and metabolites in their CNS were measured via dansyl chloride derivatization and LC-MS/MS determination. The profiling data were analyzed by multivariate statistical analyses, including principle component analysis (PCA), projection on latent structure-discriminate analysis (PLS-DA) and orthogonal projection on latent structure-discriminate analysis (OPLS-DA). Neurotransmitters and metabolites related to activation of voltage-gated sodium channels (VGSCs), N-methyl-D-aspartic acid receptors (NMDARs) and cholinergic neurotransmission were found to contribute significantly to class separation in the corresponding OPLS-DA models. Those models obtained from different exposure dosages were correlated by the Shared and Unique Structures Plot (SUS-plot) to identify appropriate variables for the construction of exposure biomarkers in the form of multivariate predictive scores. The established biomarkers for male and female medaka fish were able to predict acute sub-lethal exposure to PbTx-1 with good sensitivity and specificity (male fish: sensitivity 94.7%, specificity 80.0%; female fish: sensitivity 91.4%, specificity 83.3%). Neurotransmitter profiles in the CNS of medaka fish that should have recovered from exposure to PbTx-1 have also been determined to reveal long-term impacts to the CNS of the affected organism even after the exposure has been interrupted.

Development of a Visible Light Triggerable Traceless Staudinger Ligation Reagent.

A series of substituted 9-methylenylanthracene photocages for diphenylphosphinothioesters have been synthesized to explore their photo-uncaging properties by visible light. Substituents such as phenyl, p-trifluoromethylphenyl, p-methoxyphenyl, ethyn-1-ylbenzene, and 3,3-dimethylbut-1-yn-1-yl have been introduced in order to extend the π-conjugation of the photocage and to shift the wavelength response of the uncaging process to the visible spectral range. Among these new photocages, the (10-(3,3-dimethylbut-1-yn-1-yl)anthracen-9-yl)methyl has been shown to have the best performance in terms of fast photo-uncaging and minimal byproduct formation. It is responsive to both UV and visible photoexcitation. Quantum yields of the photoinduced heterolytic anthracenylmethyl-phosphorus bond cleavage at 366 and 416 nm were found to be 0.08 and 0.025, respectively. This photocage enables traceless Staudinger ligation to be triggered by photoirradiation in the visible spectral range for bioconjugation applications. We demonstrate this with a series of visible-light-induced oligopeptide syntheses via the conjugation of amino acid/oligopeptide building blocks by the characteristic peptide linkage attained by traceless Staudinger ligation. Yields of the resultant conjugated oligopeptides ranged from 31 to 43%. This new photocage opens up the possibility of in situ synthesis of functional proteins/peptides mediated by visible-light-induced photoclick processes for the regulation of cellular/metabolic functions of life systems.